Bug report #17138

wrong SRS identification of shapefile

Added by Tobias Wendorff over 6 years ago. Updated almost 5 years ago.

Category:Projection Support
Affected QGIS version:2.18.12 Regression?:No
Operating System:Windows 7, 64 bit Easy fix?:No
Pull Request or Patch supplied:No Resolution:end of life
Crashes QGIS or corrupts data:No Copied to github as #:25037


I often have problems with QGIS getting the right SRS out of shapefiles. Since I've got a bunch of bad results now, I'm going to write this bug report :)
Let's use OpenData datasets of the Federal Agency for Cartography and Geodesy in Germany for this.

You can get them in many projections, I'll use these:
  1. UTM32 on GRS80 (EPSG: 25832): http://www.geodatenzentrum.de/auftrag1/archiv/vektor/vg250_ebenen/2017/vg250_2017-01-01.utm32s.shape.ebenen.zip
  2. UTM32 on WGS84 (EPSG: 32632): http://www.geodatenzentrum.de/auftrag1/archiv/vektor/vg250_ebenen/2017/vg250_2017-01-01.utm32w.shape.ebenen.zip
  3. WGS84 (EPSG: 4326) : http://www.geodatenzentrum.de/auftrag1/archiv/vektor/vg250_ebenen/2017/vg250_2017-01-01.geo84.shape.ebenen.zip
These are the PRJ files:
  1. PROJCS["ETRS_1989_UTM_Zone_32N",GEOGCS["GCS_ETRS_1989",DATUM["D_ETRS_1989",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",500000.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",9.0],PARAMETER["Scale_Factor",0.9996],PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]]
  2. PROJCS["WGS_1984_UTM_Zone_32Nz",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",32500000],PARAMETER["False_Northing",0],PARAMETER["Central_Meridian",9],PARAMETER["Scale_Factor",0.9996],PARAMETER["Latitude_Of_Origin",0],UNIT["Meter",1]]
  3. GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]]
These are the results of loading the files in QGIS:
  1. EPSG:3044 [wrong]
  2. USER: 1000002 [very wrong]
  3. EPSG:4326 [correct]

EPSG:3044 actually looks like this:

PROJCS["ETRS89 / ETRS-TM32",GEOGCS["ETRS89",DATUM["D_ETRS_1989",SPHEROID["GRS_1980",6378137,298.257222101]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",9],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",0],UNIT["Meter",1]]

Since I know about EPSG-codes and projections, I'm able to correct them on export. My co-workers don't have a clue and store it in the wrong SRS. This will result into warning messages on intersections and other GIS tasks.


#1 Updated by Tobias Wendorff over 6 years ago

Correction: Ignore "2" please. I missed its +x_0=32500000, which makes it custom of course. There's leading 32 for ETRS89 only, not for WGS84. EPSG codes are a mess :(

#2 Updated by Gerhard Spieles over 6 years ago

The same problem in georeferencer. Instead of SRS 25832, QGIS produce SRS 3044.
See #13398

#4 Updated by Tobias Wendorff over 6 years ago

Returned info: it's not a Proj4 error...

#5 Updated by Tobias Wendorff over 6 years ago

I just got informed that EPSG:25833 (eastern part of German) is interpreted as EPSG:3006. In Europe, more and more cadastral offices and corporations are switching from ArcGIS & MapInfo to QGIS. Since the SRSs between EPSG:25828 and EPSG:25837 are the official ones, many users will run into problems.

Dear QGIS-guys, please fix this bug. An easy work-around is to parse gdalsrsinfo's output. It identifies SRSs from PRJ correctly.

An example (EPSG:25833), which gets read as 3006:

Update 1: The problem has not been fixed in QGIS3. From my point of view, this might be a blocker, since SRS handling is essential for a GIS.

Update 2: EvenR just has dropped me a message: "OSRFindMatches() I added in GDAL trunk a few weeks ago ( http://gdal.org/ogr__srs__api_8h.html#afb64acc80626c9ea0f9ec75017a10169 ) could potentially be of help".

#6 Updated by Tobias Wendorff almost 6 years ago

Error is still alive in QGIS3 d48818b492. This really makes trouble working with official data coming from ESRI environment :(

#7 Updated by Robert Nuske almost 6 years ago

Having imported data with CRS 25832, which gets magnled to 3044 by QGIS,
one has to pay close attention to switch the CRS back to 25832 during every export.

As far as i understood the only difference between 25832 and 3044 should be the axis ordering (north before east in 3044). Most GIS systems choose to ignore the axis ordering but not all! So it's a real source of concern that qgis assigns a wrong EPSG code to data having a perfectly fine WKT. But it seems to work fine if the prj-file contains a "AUTHORITY["EPSG","25832"]]" line, which is rarely seen in the wild.

#8 Updated by Tobias Wendorff almost 6 years ago

Robert Nuske wrote:

As far as i understood the only difference between 25832 and 3044 should be the axis ordering (north before east in 3044). Most GIS systems choose to ignore the axis ordering but not all!

One of the problems is that there are warning if two SRS on geoprocessing to not match. So if a check is run against SRS assignment, 25832 is not equal to 3044 and you'll get a warning, error or the application does an unneeded transformation (I haven't checked QGIS3, but it does on-the-fly transformations).

So it's a real source of concern that qgis assigns a wrong EPSG code to data having a perfectly fine WKT containing even a "AUTHORITY["EPSG","25832"]]" line.

Sure, that's a work-around I've posted on the mailinglist already. I'm actually having a bunch of PRJ files, which used to work on ArcGIS, PostGIS, GDAL and QGIS and I'm exchanging these if needed with a shell-script. But it is difficult to explain this to a normal employee who rarely uses QGIS. This is also an unpleasant bug for users switching from another GIS to QGIS.

When I run a processing script, I always have to check what comes in first and then reassign the SRS. Very unsightly solution.

#9 Updated by Jürgen Fischer about 5 years ago

  • Status changed from Open to Feedback

Please test with QGIS 3.4 - QGIS 2.18 reached it's end of life.

#10 Updated by Giovanni Manghi almost 5 years ago

  • Resolution set to end of life
  • Status changed from Feedback to Closed

End of life notice: QGIS 2.18 LTR


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